1. Field of the Invention
The present invention relates generally to ultrasonic medical instrumentation, and more particularly, to an ultrasonic radial focused transducer for pulmonary vein (PV) ablation.
2. Prior Art
Ultrasonic transducers are used in medical instrumentation for ablation of the pulmonary veins of the heart. A distal end of such an instrument is shown in FIG. 5, generally referred to by reference numeral 100. The instrument 100 has an outer sheathing 102 having an ultrasonic transducer 104 housed therein. The ultrasonic transducer 104 is operatively connected to an ultrasonic generator (not shown) by wiring. The ultrasonic generator may be integrally formed with the instrument or remote therefrom. The acoustic energy (alternatively referred to as ultrasonic energy or an ultrasonic wave) emanating from the ultrasonic transducer 104 is shown throughout this disclosure by dashed lines A. To fit within the geometry of the pulmonary vein, the ultrasonic transducer 104 is cylindrical in shape and can be hollow to create an air backing, as is known in the art. The acoustic intensity of the ultrasonic wave generated by the cylindrical transducer decreases with the distance from its surface (e.g., in the radial direction R as shown in FIG. 6). In the pulmonary vein ablation, the acceptable diameter of the ultrasonic transducer 104 is also limited by the application and the approach taken so that the initial power available is also limited. As a result, the acoustic energy generated by the small diameter cylindrical transducer 104 is too low at the surface of larger diameter pulmonary veins, which can be as large as 35 mm in diameter. Therefore, the acoustic energy available is not sufficient to properly ablate the surface of the larger pulmonary veins.